1. Field of the Invention
The present invention relates generally to a connecting device, or adapter, onto which an electrical unit is detachably mounted and, more particularly, to an adapter to which a portable terminal unit is electrically and/or optically connected. Also, the present invention relates to a connecting structure comprising adapters ard terminal units.
2. Description of the Related Art
Portable terminal units have been used for temporarily storing data regarding, for example, stock management in a store or a gas or electric power consumption of a user. Also, an adapter is known in the art which is effectively used in association with such a terminal unit to transmit data stored in the terminal unit through the adapter to a host computer.
FIGS. 1A to 1C show a conventional portable terminal unit 1 and a conventional adapter 5 used for the terminal unit 1. As shown in FIG. 1A, the terminal unit 1 includes a keyboard 2 for data input and a display 3 such as a liquid crystal display, both arranged on a front face of the terminal unit 1. The terminal unit 1 is also provided on the bottom end thereof with a pair of battery charging contacts 4, and on the back face thereof, opposed to the front face, with an optical interface (not shown) for data communication.
On the other hand, the adapter 5 includes a housing 6 having a generally rectangular mount surface and a plurality of guide walls 10, 11, provided respectively along longitudinally extending two edges (i.e., side edges) and laterally extending one edge (i.e., a bottom edge) of the mount surface to uprightly project from the mount surface, for guiding and positioning the terminal unit 1 in a proper position on the mount surface. The mount surface of the housing 6 and the inside surfaces of the guide walls 10, 11 define a receptive space 7 for detachably receiving the terminal unit 1 in the proper position.
The adapter 5 is also provided on the mount surface with an optical interface 8, and on the inside surface of the bottom guide wall 11 with a pair of battery charging contacts (not shown), both being aligned respectively with the optical interface and the battery charging contacts 4 of the terminal unit 1 received in the proper position. The adapter 5 further includes a foot 9 extending from the back side of the housing 6 to permit the adapter 5 to be placed with a certain inclination on a flat horizontal surface, such as a table surface, and to facilitate the mounting operation of the terminal unit 1 into the receptive space 7.
In the normal mounting operation of the terminal unit 1 on the adapter 5, the unit 1 is first incompletely placed on the mount surface of the housing 6 and is then slid thereon in a direction Y (FIG. 1A) into the proper position under the guiding function of the side guide walls 10. In this respect, the terminal unit 1 is covered on the outer peripheral region thereof with a rubber material to provide shock resistance, water resistance and an improved feel, as is commonly provided in most conventional terminal units. Therefore, it is difficult to smoothly slide the terminal unit 1 on the mount surface between the side guide walls 10 due to a relatively large friction between the surfaces of the rubber material and guide walls 10.
Also, in the conventional adapter 5, the terminal unit 1 is fully received in the proper position when the bottom end of the unit 1, on which the battery charging contacts 4 are provided, comes into abutment with the inside surface of the bottom wall 11. In this respect, it is difficult for an operator to sense the abutment between the terminal unit 1 and the bottom wall 11, and to confirm that the terminal unit 1 is fully received in the proper position.
Further, the terminal unit 1 relatively easily falls out of the receptive space 7 in the adapter 5 because the terminal unit 1 is held in its proper position mainly by gravity. This will happen, for example, when the terminal unit 1 is carelessly mounted on the adapter 5, when the protruding top end of the unit 1 incompletely placed on the mount surface of the housing 6 is inadvertently pushed down, or when an optional unit is additionally attached to the top end of the unit 1.
FIGS. 2A to 3B show certain modifications to the conventional adapter 5. In the modification of FIGS. 2A and 2B, the adapter 5 is provided with an overhanging guide wall 13 for holding the bottom end of the terminal unit 1, and a battery charging contact 14 is fixedly arranged on the mount surface of the housing 6. When the terminal unit 1 is slid on the mount surface in a mounting or detaching operation, a problem arises in that the tip end of the contact 14 may be engaged with the back face of the terminal unit 1 so that the contact 14 is inadvertently deformed or broken.
On the other hand, in the modification of FIGS. 3A and 3B, a battery charging contact 14 is fixedly arranged on the inside surface of the bottom wall 11. When the terminal unit 1 is slid along the inside surface of the bottom wall 11 in a mounting or detaching operation, a problem also arises in that the tip end of the contact 14 may be engaged with the bottom end of the terminal unit 1 so that the contact 14 is inadvertently deformed or broken.